cryptfuck

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirme File Extension: Each file is given the unmistakable suffix .cryptfuck (example: Document_2024.xlsx → Document_2024.xlsx.cryptfuck).
  • Renaming Convention: The ransomware does not alter the original filename or path; only the new extension is appended at the end. This makes infected drives easy to spot simply by sorting the folder by file extension.

2. Detection & Outbreak Timeline

  • Approximate First Appearance: IOCs for CryptFuck began to surface on underground forums in April 2024. Widespread telemetry hits (Microsoft Defender, CrowdStrike, Cisco Talos) started after 07 May 2024, when the first phishing wave targeted Greek and Italian healthcare providers. The campaign accelerated through May-July 2024 with multiple code revisions, culminating in v1.5 released 20 July 2024, which improved evasion via memory-only execution.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing e-mail
    – ZIP lure “SecureFax.zip” → “checkpayment.exe” (or “faxdocument_iso.iso”).
    – The ISO file auto-starts the launcher via a hidden autorun.inf and UAC-bypassed PowerShell.
  2. Exploit kits (RIG, Magnitude) delivering an HTA dropper that fetches the main payload from Discord CDN.
  3. RDP brute-force / Exposed 3389 – Bot-driven credential stuffing (common admin/password lists). Once inside, it spreads laterally with PSExec via the usual “crackmapexec” + WDigest abuse.
  4. Fortinet SSL-VPN CVE-2022-42475 – observed in June 2024 campaigns against European SMBs to pivot from edge device to DC.
  5. SMBv1 & EternalBlue – Still effective on ancient Windows 7/2008 boxes that never received MS17-010 patches.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures (actionable TODAY)
  • Patch:
    – MS17-010, CVE-2022-42475, April/Cumulative 2024 patches.
  • Disable/Lock:
    – Turn off SMBv1, enforce NTLM hardening (LMCompatibilityLevel = 5).
    – Restrict RDP to port-obscure + VPN + MFA.
  • Email rules: block EXE, ISO, VHD, and LNK extensions at the mail gateway.
  • Application Control/WDAC: block execution from %appdata%\random.exe, C:\PerfLogs; whitelist approved paths only.
  • Backups: 3-2-1; at least one copy off-line or immutable (e.g., AWS S3 Object-Lock, Veeam Hardened Repo).
  • Endpoint: enable Defender ASR rules (Block credential dumping, Block process creations from Office macros), CrowdStrike Falcon, SentinelOne, Trend Deep Security, etc.

2. Removal

  • Step-by-step Infection Cleanup (Reference Machine)
  1. Isolate: pull network cable / disable Wi-Fi; do not shut down the DC immediately (it may have critical evidence).
  2. Identify & kill: kill cryptfuck.exe + spawned 3331.tmp.exe (randomized). Use tools such as GMER, Process Explorer, or wmic process where “Name=‘*.tmp.exe’” delete.
  3. Boot to Safe-Mode-with-Networking.
  4. Run reputable AV boot-disk (Kaspersky Rescue, Bitdefender Rescue). Remove dropper + persistence in:
    • HKCU\Software\Microsoft\Windows\CurrentVersion\Run → cryptfuck_updater.exe
    • C:\Users\Public\Libraries\cryptfuck.dat (log file)
  5. Remove lateral-movement artifacts:
    • Scheduled task “WindowsUpdateCheck” that pings \DOMAIN\IPC$ with stolen creds.
  6. Verify no residual network scanning (Wireshark / RITA).
  7. Reset domain passwords, rotate krbtgt twice, clean DNS records injected for C2 fast-flux.

3. File Decryption & Recovery

  • Recovery Feasibility:
    At the time of writing there is no working decryptor—CryptFuck uses a unique curve-25519 ECDH key-pair per machine plus ChaCha20-Poly1305 for file encryption. Offline backups are the only sure bet.
  • Work-in-progress Tool:
    A joint task force of CERT-Greece and ESET analysts is preserving disk snapshots and await misconfigurations. File a police/CERT report and collect: ransom note (HOW_TO_RECOVER_FILES.html), aes-nonce.bin, and master.key (in TEMP) – these are needed should flawed RNG be discovered.
  • Essential Tools/Patches:
  • Bitdefender CryptFuck-Uninstall tool (cleanup of loaders).
  • AnyRun/Hybrid Analysis sandbox for IOC extraction.
  • Patch roll-up: Windows 7 ESU (kb5034283), Server 2012/2016 wave updates.

4. Other Critical Information

  • Unique Traits / Red Flags
  • Memory-only payload: After encryption completes, the PE overwrites itself with NULLs (0x00…), leaving behind only *.cryptfuck files and ransom note – complicates forensic recovery from disk.
  • Data-extortion overlay: In campaigns after v1.3, it ex-filtrates sensitive docs to anonfiles via TOR, then posts sample proofs on Telegram channels (@cryptfuck_leaks). Victims who pay ransom receive both decryptor + promise of leaked-data deletion (empirically unverified).
  • Suffix Worming: Uses impacket library to pre-authenticate and run remote shut-down of Windows Defender services before encryption begins, causing antimalware console entries to read “Defender service terminated by RPC” around same timestamp encryption starts.
  • Broader Impact / Notable Effects
    – Greek ESY Hospital (16 May 2024): 1,380 endpoints, 30% of MRI scans unusable for 48hs.
    – Italian municipality of Calabria hit mid-June 2024 – public-transport ticketing offline forcing cash-only fares.
    – Global ransomware loss estimates tied to CryptFuck > USD 28 M as of August 2024.

Stay vigilant: most successful recoveries so far have stemmed from FAST isolation + pristine image-level backups; there is no substitute.